This invention relates to a method of producing tofu-like food from soybeans as raw materials.
Tofu or a soft vegetable cheese prepared from soybean milk has been widely used as a precious protein-rich food in Japan, and is expected to acquire world-wide demand. The conventional method for producing such tofu generally includes first washing material soybeans with water, immmersing and swelling them in water, crushing, watering and heating the swollen soybeans, and then filtering them to obtain soybean milk. The resultant residue is called "okara". Such soybean milk is coagulated by a coagulant, e.g. a calcic salt such as calcium sulphate, a separated solution (called "yu") is removed, the coagulated milk is poured into a mold box, a pressing lid is placed thereon for pressurization, additional "yu" is removed, and then the resultant solidified milk is placed in a water bath for water bleaching.
In such conventional method, the "okara" and "yu" portion produced at time of coagulation and forming are to be abandoned, so that the yield of the final products is as low as about 50%. These "okara" and "yu" portion, however, contain a great quantity of nutriment therein. For example, the "okara" still contains 30% or more solid matter, 20% or more of protein, 30% or more of fat, and 50% or more of carbohydrates as compared with the respective ingredients contained in the soybeans. Meanwhile, the "yu" portion also contains e.g. 30% or more of carbohydrates, 50% or more of ash, 40% or more of calcium and other ingredients as compared with the respective ingredients contained in the soybeans.
In these remaining ingredients are contained organic nitrogenous compounds, such as various amino acids and peptide, and low molecular carbohydrates, such as sucrose, vitamins as well as highly nutritious high molecular compounds, such as albuminous protein and hemicellulose. Meanwhile, the abandoned "yu" portion has become a source of contamination of rivers, requiring waste water disposal plants.
Further, the tofu may be available as the so-called "frozen tofu" if it is subjected to further freezing and ripening for spongy texturization and dried, having a required softening treatment with liquid ammonia or a water (called "kansui") mixed with potassium carbonate and sodium carbonate at time of cooking because of the aforementioned coagulation with salts at time of production. However, such softening process is not desirable because the liquid ammonia or "kansui" would throw the original nutrition of the soybeans off balance.